Scott, The -.210 v one the multiplier is OK for now. The tube value is for when the tube was originally tested. As the electron multiplier in the tube ages the required voltage needs to be increased (up to a maximum of 2500VDC). If you have a manual I would suggest that you do the low frequency test. It takes a frequency at 1/2 the zeeman frequency that you apply to a pin on the underside of the unit on the long terminal board. This allows you to test the tube even if the RF circuitry is at fault. If the low frequency test fails then before blaming the tube you need to get in and measure the ionizer voltage (older units a 1VRMS square wave, new units 1VDC) and also measure the mass spectrometer voltage with the pot at max CW (about +17 to 18VDC. If everything checks out but low freq. test still fails increase the EM voltage to 2500VDC and repeat the test. If no low frequency response by now the tube has a high probability if beaing dead! If the test is good then your problem lies in the RF circuitry somewhere. Corby Dawson ____________________________________________________________ Click here to find affordable degree programs. http://thirdpartyoffers.juno.com/TGL2141/fc/Ioyw6i3l8Op2dKMrmSXhHChrYqlJXFP6LXoDtx9dtYTJzdmc3WCvct/

How does one increase the EM voltage? I do have the manual and I have done the LF test but the ionizer and mass spec voltages were what I was looking for On Tue, Sep 30, 2008 at 1:11 PM, corby d dawson <cdelect@juno.com> wrote: > Scott, > > The -.210 v one the multiplier is OK for now. The tube value is for when > the tube was originally tested. As the electron multiplier in the tube > ages the required voltage needs to be increased (up to a maximum of > 2500VDC). > > If you have a manual I would suggest that you do the low frequency test. > > It takes a frequency at 1/2 the zeeman frequency that you apply to a pin > on the underside of the unit on the long terminal board. > > This allows you to test the tube even if the RF circuitry is at fault. > > If the low frequency test fails then before blaming the tube you need to > get in and measure the ionizer voltage (older units a 1VRMS square wave, > new units 1VDC) and also measure the mass spectrometer voltage with the > pot at max CW (about +17 to 18VDC. > > If everything checks out but low freq. test still fails increase the EM > voltage to 2500VDC and repeat the test. > > If no low frequency response by now the tube has a high probability if > beaing dead! > > If the test is good then your problem lies in the RF circuitry > somewhere. > > Corby Dawson > ____________________________________________________________ > Click here to find affordable degree programs. > http://thirdpartyoffers.juno.com/TGL2141/fc/Ioyw6i3l8Op2dKMrmSXhHChrYqlJXFP6LXoDtx9dtYTJzdmc3WCvct/ > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >